Sudoku is Stepping Stones by Gray Kanarek, App variant is SANDWICH


Fill the grid such that each row, column, and orthogonally-connected 9-cell region contains each of the digits 1-9 with no repeats. Region borders must be deduced (though one is given). Clues outside the grid give the sum of the first digit seen in each successive region in that row or column. **The summed digits always appear in increasing order.**